Screw head driver slot having unequal torque areas



April 20, 1965 A. E. BORUP 3,178,988

SCREW HEAD DRIVER SLOT HAVING UNEQUAL TORQUE AREAS Filed Dec. 25. 1963 2 Sheets-Sheet l I Tg-i IN VE'N'T'UF' Fl. 5'. BURL! April 20, 1965 A. E. BORUP ,178,

SCREW HEAD DRIVER SLOT HAVING UNEQUAL TORQUE AREAS Filed Dec. 23, 1963 2 Sheets-Sheet 2 United States Patent 3,17 8,988 SCREW HEAD DRIVER SLOT HAVING UNEQUAL TORQUE AREAS Alfred E. Borup, Cranford, NJ., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed Dec. 23, 1963, Ser. No. 332,501 2 Claims. (Cl. 85-45) This invention relates to screws and the like, and particularly to new and useful improvements in the head portions of screws. The present application is a continuation in part application based upon an earlier filed copending application by the same inventor, Serial No. 74,955, filed December 9, 1960 now abandoned.

Many types of screw heads have been suggested wherein the head is shaped to facilitate the application of a driving torque. Some heads have been formed so that the screwdriver bits may be locked within the slots formed on the heads. Many ramifications of such designs have appeared in an attempt to attain better slotted heads for receiving the thrust and torque of either manual or automatic driving tools. In some instances, the slotted head was shaped so that a high degree of torque could be applied to drive the screw, but such designs permitted little, if any, application of torque thereon for removing the screw. In other instances, the designs were quite complicated which resulted not only in weakened and fragile screw heads but also required a special type screwdriver for insertion of the screw.

The object of this invention is a screw obviating the above difiiculties and having a head which is simple in design and far stronger than the head of a conventional screw for enabling a greater application of thrust and torque to the head either by manual or automatic driving tool-s.

Broadly, a screw according to the object is provided with a head having a slot having two pairs of diagonally opposed side walls, with one pair of extending higher and having a greater surface area than the other pair of walls.

In a preferred embodiment, the screw head has a transverse slct which is wide at the ends but tape-rs towards a central indentation provided for receiving the boss of a driving bit to guide and hold the bit in the slot. The upper surface of the head is contoured so that the sid walls of the slot which receive the driving thrust are higher than the opposite walls to facilitate the automatic engagement of a rotating driving bit into the slot. The higher side walls also permit the application of greater torque thereon for insertion of the screw and the lower walls on the opposite sides of the slot provide sufiicien-t area for the thrust required to remove the screw. Even though the screw has been described particularly for use with a special automatic tool, it is understood that a common screwdriver can also be utilized.

Other objects and a fuller understanding of the invention may be had by referring to the follow description and claims taken in conjunction with the accompanying drawings in which:

FIG. 1 is an isometric view of a punch utilized for forming the head portion of the screw;

FIG. 2 is an isometric view of the head portion of the screw;

FIG. 3 is a front view of the screw as seen through the longitudinal axis of the slot;

FIG. 4 is a view of the screw as seen along the lines 4-4 of FIG. 3; and

FIG. 5 is a view of the screw as seen along the lines 55 of FIG. 4.

With regard to the drawing, reference character indicates generally the shank or stem of the screw which is provided with a head 11. The shank may be either the "ice machine, metal, or wood screw type and may be provided with threads of suitable character. Likewise, the head 11 may be either the round type, as illustrated, or of the polygonal or any other preferred type.

The configuration of the head (described in more detail hereinafter) may be shaped by the use of a conventional cold punching method with a punch 20 having the contour of the desired head configuration. This method eliminates a separate screw slotting operation and produces a substantially stronger screw head 11 due to the natural cold grain flow lines in the material which follow the contour of the cold forged punch and remain intact around the slot 23. Advantageously, the aforementioned punching operation also prevents the formation of nudesirable burrs along the edges 24 of the slot 23.

In the embodiment shown the screw head is formed with a transverse slot 23 or recess having a flat bottom surface 12, the slot bisecting the head 11 substantially perpendicularly to the axis of the shank 10. The slot 23 extends to the periphery of the head, its end portions 13 being wide but tapering towards the mid-section 14 of the slot, to resemble a dove-tail configuration.

An indented dimple 15 is inclined downwardly from the top surface 16 of the head 11 to the flat bottom surface 12 in coaxial relationshipto the shank 10. With such an indentation. the screw is particularly adaptable for receiving a boss on the driving bit of an automatic driving tool to guide and hold the bit in the slot. However, it is understood that a conventional manual screwdriver can also be utilized more effectively with this novel screw than conventional type screws due to the increased strength of the side walls, now to be described. As a further advantage, the convex dimple 26 on the forming punch 20 also strengthens and prolongs the life of the punch.

The slot 23 has a pair of diagonally opposed side walls 171=7 which extends from the indented dimple 15 to th periphery of the head 11. The walls 17-17 project upwardly from the flat surface 12 higher than the other pair of diagonally opposed side walls 18- 18. As shown in the drawings the respective surfaces of each pair of side walls 17- 17 and 18-18 lie in substantially parallel offset planes and the surfaces of one pair of side walls are angularly displaced in relation to the surfaces of the other pair of side walls. With such a structural arrangement, the high side walls 1717' intercept a rotating driving bit advanced thereagainst by the contour of the head 11 to result in the bit automatically engaging the slot. Also, the high walls 17-17 are strengthened having a greater surface area than the walls 18 18 to receive a greater driving thrust of the bit as well as for permitting greater torque thereon for insertion of the screw. As indicated in FIG. 5, the substantially greater surface area of the diagonally opposed side walls 17417 is concentrated in a region between a plane 2 1 defined by the shank surface and a plane 22 defined by a closer extremity of the slot 23.

The material displaced from the slot 23 and indented dimple 15 is shifted in such a manner to form a head 11 having greater strength than conventional type screws. The material displaced from the dove-tail end portions is shifted not only to give greater strength to the walls 17-17 but also to permit an easier engagement of the rotating bit in the slot. Further, the additional strength provided in the side walls 17-17 for receiving the driving thrust is obtained without sacrificing the material needed to form the walls 18 18 to provide the surface area need for the application of torque thereon for removal of the screw.

:It is to be understood that the above-described arrangements are simply illustrative of the application of the prin- :ciples of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. -A screw comprising:

a shank,

a head extending beyond said shank and having a flatbottomed transverse driving slot extending completely across the diameter of the head beyond the opposite sides of the screw shank with one pair of diagonally opposed side walls of the slot having a greater surface area and extending higher than the other pair of diagonally opposed side walls,

said head having a semiconically shaped indentation formed on the upper surface of each pair of adjacent side walls with the vertex thereof in the plane of the fiatabottomed slot substantially midway between said side walls,

each of said higher side walls with said greater surface area including a first region located between limits defined by a plane perpendicular to said higher wall,

and coincident with the shank surface and by the closer extremity of the slot to accommodate a rotatable driving torque, said first region having a surface area substantially greater than the surface area of a second immediately adjacent region located between said plane and said vertex of said semiconically shaped indentation,

the width of the slot gradually increasing from its mid section toward the end portion thereof.

2. A screw comprising:

a stem with a head,

the head having a driving slot extending completely across the diameter thereof with a flat bottom surface biseoting the head substantially perpendicularly to the axis of the stem,

the slot being wide at its end portions and tapering towants a substantially central conically shaped indentation inclined downwardly from the top surface of the head towards the flat bottom surface for receiving the boss of a screwdriver bit, the vertex of said conically shaped indentation being in the plane of the surface of the fiat bottom slot, said slot and said indentation forming two pairs of diagonally opposed side walls in said head, each pair extending laterally from the indentation to the end portions,

one pair of side walls projecting higher from the fiat bottom surface than the other pair and having a greater surface area,

each of said higher side walls with said greater surface area including a first region for receiving the driving thrust of a screwdriver bit, said first region having a surface area substantially greater than a second immediately adjacent right-triangularly shaped region defined by the vertex of said conically shaped indentation and a line formed by the intersection of the surface of said conically shaped indentation with said higher side wall, and

the contour of the top surface of the side walls being convexly curved downwardly from the central indentation towards the periphery of the head to earn the screwdriver bit into engagement with the side walls.

References Cited by the Examiner UNITED STATES PATENTS 2,106,278 1/38 Redmer -45 2,182,568 :12/ 39 Olson 85-45 2,431,628 11*1/47 Wa'arioh 85-45 2,556,155 6/51 Stellin 85-45 2,954,7ll9 1-0/60 Vaughn 85-45 EDWARD C. ALLEN, Primary Examiner. 

1. A SCREW COMPRISING: A SHANK, A HEAD EXTENDING BEYOND SAID SHANK AND HAVING A FLATBOTTOMED TRANSVERSE DRIVING SLOT EXTENDING COMPLETELY ACROSS THE DIAMETER OF THE HEAD BEYOND THE OPPOSITE SIDES OF THE SCREW SHANK WITH ONE PAIR OF DIAGONALLY OPPOSED SIDE WALLS OF THE SLOT HAVING A GREATER SURFACE AREA AND EXTENDING HIGHER THAN THE OTHER PAIR OF DIAGONALLY OPPOSED SIDE WALLS, SAID HEAD HAVING A SEMICONICALLY SHAPED INDENTATION FORMED ON THE UPPER SURFACE OF EACH PAIR OF ADJACENT SIDE WALLS WITH THE VERTEX THEREOF IN THE PLANE OF THE FLAT-BOTTOMED SLOT SUBSTANTIALLY MIDWAY BETWEEN SAID SIDE WALLS, 